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Science · 2025 · 3 marks
CBSE 2025 · Region 5 · Set 1 · Q31
The power of a lens is -0.25 D. Based on this information, find out (a) The type of lens and its focal length. (b) The eye defect for which it may be…
The power of a lens is -$\displaystyle 0.25$ D. Based on this information, find out
(a)
The type of lens and its focal length.
(b)
The eye defect for which it may be used as a corrective lens.
(c)
The nature and size of the image formed by this lens when an object is placed between F and 2F from the optical centre of this lens.
Marking-scheme solution
(a) Concave lens
\[\mathrm{P}=\frac{\mathbf{1}}{\mathbf{f}(\boldsymbol{m})} \Rightarrow \mathrm{f}=\frac{\mathbf{1}}{-\mathbf{0 . 2 5}} \Rightarrow \mathrm{f}=-4 \mathrm{~m}
\]
(b) Myopia
(c) Virtual , Erect Diminished
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CBSE Class 10 Science past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.